Apparatus for passive removal of subsurface contaminants and mass flow measurement

ABSTRACT

A system for improving the Baroball valve and a method for retrofitting an existing Baroball valve. This invention improves upon the Baroball valve by reshaping the interior chamber of the valve to form a flow meter measuring chamber. The Baroball valve sealing mechanism acts as a rotameter bob for determining mass flow rate through the Baroball valve. A method for retrofitting a Baroball valve includes providing static pressure ports and connecting a measuring device, to these ports, for measuring the pressure differential between the Baroball chamber and the well. A standard curve of nominal device measurements allows the mass flow rate to be determined through the retrofitted Baroball valve.

[0001] The U.S. government has rights in this invention pursuant tocontract number DE-AC09-96SR18500 between the U.S. Department of Energyand Westinghouse Savannah River Company.

FIELD OF THE INVENTION

[0002] This invention relates generally to systems for passive removalof subsurface contaminants and flow measurement. More specifically, thisinvention is a passive removal valve apparatus for removing subsurfacecontaminants integrated with a volumetric flow meter.

BACKGROUND OF THE INVENTION

[0003] Contaminants can exist in subsurface soil and groundwater in theliquid or vapor phase as discrete substances and mixed with and/ordissolved in groundwater and soil gases. Various contaminants can befound in groundwater and soil, such as volatile compounds, includingvolatile organic compounds, nonvolatile materials, and metalcontaminants. Such contaminants can be found and dealt with in thevadose (unsaturated) zone found between the surface of the earth and thewater table, at the interface between the vadose zone and the watertable, and in the saturated zone below the water table.

[0004] There are many proposed methods for removal of surfacecontaminants, such as excavation followed by incineration, in situvitrification, biological treatment, chemical additives fordeactivation, radiofrequency-heating, etc. Although successful in someapplications, these methods can be very expensive (hundreds of dollarsper ton) and are not practical if many tons of soil must be treated.

[0005] One example of low cost, efficient contaminant extraction isdisclosed in U.S. Pat. No. 5,641,245 to Pemberton et al., which isincorporated herein by reference. The Pemberton patent discloses anapparatus for passively removing subsurface contaminants. The apparatusprovides a means for opening and closing a valve (the “Baroball” valve)as the atmospheric and subsurface pressures differ from one another.Basically, the apparatus allows a well to breathe out contaminantsduring low atmospheric pressure.

[0006] The apparatus includes a riser pipe extending through a well intothe ground reaching a position above the water table, where contaminantsare likely to be present. The end of the pipe positioned above the watertable contains perforations allowing contaminant vapors to enter thepipe. A portion of the riser pipe extends upward above the ground and isin fluid communication with a valve. The valve is formed to have a lowcracking pressure and is responsive to changes in ambient atmosphericpressure.

[0007] The Baroball valve is formed from a vertically oriented chamberhaving a conic shaped valve seat. A ball is disposed in the valvechamber and rests on the valve seat when equalization of atmospheric andsubsurface pressure exists. Cracking pressure, the pressure required tolift the ball, is related to the density or weight and surface area ofthe ball and is preferably no more than about one mbar. As subsurfacepressure rises above atmospheric pressure the ball rises in the valvechamber allowing contaminants to escape through the valve out into theatmosphere.

[0008] The benefits of the Baroball valve are numerous. The valveprovides passive release of contaminants from a well with minimalconstruction costs, maintenance, and operation costs, and additionallyrequires no external energy source. The Baroball valve further preventsthe flow of air into a well, and thereby increases the amount ofcontaminants that are released during periods of low pressure bypreventing dilution of contaminants in the well. The valve enclosure isalso transparent, semi-transparent, or is formed to have a window, sothat malfunctioning of the apparatus can be visually detected. Thus, thevalve provides a low cost method of removing subsurface contaminants.

[0009] However, there are disadvantages associated with the Baroballapparatus. Although the Baroball valve provides passive release ofsubsurface contaminants, it does not provide a mass flow measurement ofthe amount of contaminants released through the valve. Therefore, anexternal measuring device must be used to measure the mass flow throughthe valve. Many external apparatuses, for attachment to the Baroballvalve, exist for measuring mass flow through the valve mechanism.Several are discussed below.

[0010] U.S. Pat. No. 4,873,873 to Day discloses a system for meteringthe flow rate of air through a duct in which gates are pivotally mountedand connected together to vary the area of the duct. The gates arebalanced so as to be effectively weightless. The forces on and thepositions of the gates correspond to the pressure and the flow rate inthe duct.

[0011] U.S. Pat. No. 5,616,841 to Brookshire is directed to a meteringpipe system that is positionable in fluid communication with a well in alandfill for determining gas flow rate through the well. The deviceincludes an upstream segment and a downstream segment coupled togetherand separated by an orifice plate. Specifically, the segments areadvanced into the coupling toward each other, on opposite sides of theorifice plate from each other. Upstream and downstream pressure portsare respectively formed through the walls of the upstream and downstreamsegments and the coupling adjacent the orifice plates. The difference inpressure at the ports is correlated to a flow rate through the pipe.

[0012] U.S. Pat. No. 4,559,834 to Phillips et al. is directed to a flowmeter arrangement including an elongated body adapted to be disposed inan upright position with a typical rotameter design utilizing a floatingball mechanism. The flow meter design has a first valve at the base ofthe rotameter tube and a second valve at the top of the rotameterchamber. The flow meter arrangement can be adapted for pressure orvacuum applications.

[0013] U.S. Pat. No. 5,099,698 to Kath et al. is directed to anelectronic readout for a rotameter flow gauge which includes a means foroptically scanning the rotameter flow gauge and determining the positionof a float within the rotameter.

[0014] Finally, U.S. Pat. No. 5,379,651 to Doolittle is directed to animproved electronic monitoring arrangement for a rotameter deviceutilizing a single point source of radiation at one side of therotameter and a vertical array of detectors diametrically opposite toit. The elevation of the radiation source is identical to the uppermostelevation of the radiation detectors. The elevation of the rotameterfloat will intersect the vertical array of detectors allowing for areading of the flow rate.

[0015] The above references provide systems and methods of measuringairflow mass. However, each requires that it be attached to the passivecontaminant removal system. An external flow meter device placed influid communication with the passive valve is disadvantageous forseveral reasons.

[0016] First, the passive valve is just that, passive. The Baroballvalve requires no external power source. Thus, multiple valves can bedeployed in the field without building an infrastructure for providingpower to the removal system. Most flow-meter systems require an externalenergy source for powering the measuring device. Therefore, allelectronic flow meters requiring external energy diminish the advantagesgained by a passive system. Although flow meters exist that do notrequire external energy sources, these devices like their electroniccounterparts cause back pressure that hinders the operation of thepassive valve.

[0017] The Baroball system operates in a very narrow pressuredifferential range, generally a few mbars. A mbar change in pressure cancause the valve to open, releasing contaminants. Therefore, any backpressure or airflow constriction caused by an external flow meter devicecan cause the valve to malfunction. Additionally, one advantage of theBaroball system is to provide a low cost and low maintenance contaminantremoval option. Thus, external flow meter devices add unnecessaryexpense; thereby defeating the Baroball system's low cost advantage.

[0018] Consequently, a need exists for a passive removal system forsubsurface contaminants including a mass flow meter such that the massflow meter operates without hindering operation of the valve or addingunnecessary costs.

SUMMARY OF THE INVENTION

[0019] This invention relates to an improvement on the Baroball valve.In one embodiment, the valve mechanism of the Baroball is modified toserve as a rotameter bob. Additionally, the valve seat and walls aremodified to form the measuring chamber. In a second embodiment, deployedBaroball valves are retrofitted to include two ports, one on each sideof the valve and in fluid communication with a static pressure device.The flow rate, through the valve, is proportional to the pressure dropacross the device.

[0020] Among objects of this invention are to:

[0021] provide a passive subsurface contaminant removal system thatmeasures the mass flow of contaminants passing through the valve;

[0022] provide a method to retrofit an existing Baroball valve so itmeasures mass flow of the contaminants passing through the valve; and

[0023] provide a mass flow-measuring device that does not hinder theoperation of the Baroball valve.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 shows an exemplary passive removal apparatus including animproved Baroball valve of the present invention as deployed in a well.

[0025]FIG. 2 shows a cross sectional view of the Baroball valve of FIG.1; and

[0026]FIG. 3 shows a cross sectional view of a retrofitted Baroballvalve for measuring mass flow through the valve.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 discloses a passive contaminant removal apparatus deployedin a well. Apparatus 5 includes a riser pipe 10 with a lower perforatedsection 12 and top end 11. Riser pipe 10 extends downward into thesubsurface 13 through a well 14 to a point just above the water table20. The perforated section 12 of riser pipe 10 is placed in the vadosezone where the unwanted contaminants exist. Perforations 12 may beformed in the vertical, horizontal or diagonal direction on riser pipe10. Perforations 12 may also be created by forming a plurality of holesin riser pipe 10 or by cutting away the bottom portion of riser pipe 10and affixing a screen across the opening of the pipe.

[0028] At the surface 15, a well head 16 is formed to seal riser pipe 10in well 14. This seal also prevents air from seeping into well 14.Preferably, well head 16 is formed from a layer of concrete including anaperture 17 for receiving the riser pipe 10 into well 14. Prior toforming the well head 16, well 14 in an area between riser pipe 10 andwell wall 18 may be packed with sand, bentonite and/or grout as is wellknown to those skilled in the art. A seal (not shown) may be interposedbetween riser pipe 10 and aperture 17. Riser pipe 10 may be formed fromany solid material, but is preferably formed from a non-corrosivenon-porous material that does not absorb gaseous contaminants.Preferable materials for riser pipe 10 include stainless steel, Teflon,and polyvinyl chloride (PVC).

[0029] Top end 11 of riser pipe 10 terminates above the well head 16forming a pipe end 19 for receiving a valve 30. The valve 30 can becoupled to top end 11, in any appropriate manner as, for example, bythreads or glue.

[0030] Referring to FIG. 2, a preferred embodiment of a modifiedBaroball valve 30, including a flow meter will be described in detail.Valve 30 comprises a chamber 31 and exhaust pipe 40. Chamber 31 includesan interior chamber 32 formed from a sloping interior wall 33. Interiorchamber 32 is conical in shape with a wide top end 34 and a narrowervalve seat 35. Top end 34 includes an aperture 36 for receiving anexhaust pipe 40. Valve seat 35 also includes an aperture 37 in fluidcommunication with top end 11 of riser pipe 10.

[0031] Valve seat 35 is formed to receive a ball 38. The conical shapedinterior chamber 32 forms a rotameter measuring device. Ball 38 ofchamber 31 is formed to be lightweight so that a slight pressuredifferential between the atmosphere 41 and well 14, for example, onembar, causes the ball 38 to lift from valve seat 35. Ball 38 is madefrom a smooth lightweight non-porous material such that the ball 38forms a tight seal when in communication with valve seat 35. Syntheticmaterials are preferred and ball 38 may be a commercially availabletable tennis ball.

[0032] Chamber 31 is formed from a non-porous non-corrosive solidmaterial such as stainless steel, Teflon, polyvinyl chloride (PVC),polycarbonate or butyrate with dimensional stability and resistance toweathering. Chamber 31 is made of a transparent material or contains awindow so that the flow meter can be monitored and readings can betaken. The top end diameter, D1, valve seat diameter, D2, and height, H,of the inner chamber 32 is determined using design guidance associatedwith rotameter devices, as is well known by those skilled in the art.The flow through rotameter interior chamber 32 is a function of thevolume, surface area, and density of ball 38, the annular area ofinterior chamber 32, the drag coefficient, the gravitational constant,and the fluid density through valve 30, as is well known by thoseskilled in the art. A uniform taper of interior chamber 32 is a functionof D1, D2, H and Y, a reference height of ball 38 in chamber 32,although other variations on the taper are possible. Chamber 32 containsmarkings (not shown) which indicate the mass flow through the valve 30.Thus, as contaminants flow through valve 30 causing ball 38 to be liftedup into chamber 32, the intersection of ball 38 and a marking on chamber31 determines the mass flow through valve 30.

[0033] Valve seat 35 of chamber 31 can be of the same material aschamber 31 or can be formed from a soft and resilient material, forexample, silicones, rubbers, etc. for increasing the sealing actionbetween ball 38 and valve seat 35. Furthermore, valve seat 35 can beformed by placing a washer at the bottom of the interior chamber whereinthe washer forms a seat for ball 38.

[0034] Cracking pressure, the pressure causing ball 38 to separate fromseat 35, is dependent on the density or weight and surface area of ball38. The cracking pressure should be as low as possible so that the valveworks with the slightest differential in atmospheric 41 and well 14pressure. A valve 30 having a higher cracking pressure, up to thirtymbars or more will also be useful in an apparatus for extractingcontaminants from a subsurface. When ball 38 is a table tennis ballcracking pressure is about one mbar.

[0035] Valve seat 35 comprises an aperture 37 through which air flowswhen valve 30 is cracked. Air stream, indicated generally by 42 helpslift ball 38. It is also recognized that if atmospheric 41 pressure isgreater than well 14 pressure, ball 38 will be forced down onto seat 35forming a seal blocking any reverse air flow into well 14. If reverseair flow were allowed into well 14, the air would be forced to travelthrough subsurface 13 surrounding the well. Air that enters subsurface13 during high atmospheric pressure will dilute contaminated air in well14 causing less contaminated mass to be released during periods of lowatmospheric 41 pressure.

[0036] Top end 34 of chamber 31 is formed to receive exhaust pipe 40through which contaminated gases from well 14 exit into atmosphere 41.Exhaust pipe 40 may be glued, or otherwise connected to top end 34.Exhaust pipe 40 may be bent such that precipitation does not easilyenter chamber 32 through pipe 40. The top end of exhaust pipe 40 mayalso contain a screen (not shown) so that insects cannot enter chamber32 and hinder the operation of valve 30.

[0037] The preferred embodiment, as shown in FIGS. 1 and 2, comprises acompartmentalized apparatus 5. The apparatus is formed by riser pipe 10,valve 30 and exhaust pipe 40 that are coupled together. The modularityof the apparatus makes the apparatus easy to assemble and disassemble.Disassembly and reassembly may be required for maintenance purposes.Given the assembly's modularity, it is seen that apparatus 5 can bedisassembled, repaired, cleaned and restored to operation if suchproblems arise.

[0038]FIG. 3 discloses a Baroball valve that is retrofitted to allowmass flow through valve 50 to be measured. The retrofitting of deployedBaroball valves 50 requires pressure ports 56 and 57 to be formed in theupper chamber 52 and in the top end 11 of riser pipe 5 of valve 50,respectively. A static pressure measuring device 55 is then placed inparallel to valve 50 for measuring the pressure differential betweenriser pipe 5 and upper chamber 52. Development of a standard curve fornominal device positions allows flow rate to be determined through valve50.

[0039] In either embodiment, an electronic data storage mechanism (notshown) can be added for recording flow measurement over a period oftime, as is well known to those skilled in the art.

[0040] The foregoing is provided for purposes of illustrating,explaining, and describing embodiments of the present invention thatprovides a system for improving and method for retrofitting the Baroballvalve. Modifications and adaptations to these embodiments will beapparent to those skilled in the art and may be made without departingfrom the spirit of the invention or the scope of the following claims

What is claimed:
 1. An apparatus for removing contaminants from an areaof the subsurface and measuring an amount of contaminant flowing throughthe apparatus, the subsurface having a well formed therein, theapparatus comprising: a. a riser pipe having a first end and a secondend, the first end having an aperture thereat and in use extendingthrough the well into the subsurface and the second end rising up abovethe ground in use; b. a valve in fluid communication with the second endof the riser pipe, the valve comprising: (1) a chamber with verticallyextending walls; (2) a sealing mechanism; (3) a valve seat formed at thebottom of the chamber for receiving the sealing mechanism; and (4)measurement markers on the vertically extending walls for determiningthe flow rate through the valve wherein the valve opens and closes whenthe atmospheric pressure is different than the pressure of thesubsurface area and the flow rate is measured by the height of the ballin the valve chamber relative to the measurement markings.
 2. Theapparatus of claim 1 , further comprising a ball as the sealingmechanism disposed in the chamber, the ball having a proper mass andsurface area such that a drop in pressure between the atmosphere and thesubsurface causes the ball to lift from the valve seat allowing the wellto breathe out into the atmosphere.
 3. The apparatus of claim 1 ,wherein the first end of the riser pipe has a plurality of aperturesthereat for allowing subsurface contaminants to enter the pipe.
 4. Theapparatus of claim 2 , wherein the vertically extending chamber wallsform a flow channel, the channel serving to direct a stream ofcontaminants through the apparatus for which the flow rate is to bemeasured.
 5. The apparatus of claim 4 , wherein the ball for sealing thevalve is flow responsive and movable within the flow channel in responseto varying flow rates of the subsurface contaminant stream.
 6. Theapparatus of claim 5 , wherein the vertically extending chamber wallsare transparent so a user can determine the height of the flowresponsive ball in the chamber.
 7. A method for retrofitting a Baroballvalve to allow for mass flow measurements, the method comprising: a.forming a first static pressure port in a chamber housing a valvemechanism; b. forming a second static pressure port in a riser pipe influid communication with the chamber; c. connecting the first and thesecond pressure port to a pressure measuring device; and d. reading thepressure measuring device and comparing the reading to a standard curvefor determining the mass flow through the valve.